United States Patent: 4159310

Our headline won't at first seem to match up well with the content accessed via our opening link, above; but, we assure you, it all ties in, as should become apparent.

In a recent news article concerning the campaign by West Virginia's elected representatives to forestall the short-sighted and wasteful classification of Coal fly ash as a hazardous waste by the US EPA:

Senators Supporting Fly Ash Bill - News, Sports, Jobs - The Intelligencer / Wheeling News-Register;

it was reported that:

"West Virginia's Democrat senators are supporting a bill to stop fly ash from being regulated as a hazardous material by the Environmental Protection Agency.

Sens. Jay Rockefeller and Joe Manchin are among the original co-sponsors of House Bill 2273, the "Coal Residuals Reuse and Management Act." The measure was first introduced in the House by Rep. David McKinley, R-W.Va.

Manchin ... said the material has been used in Marshall County by the CertainTeed company to make gypsum board used by the construction industry. "


First of all, we'll note that making gypsum board isn't the only thing CertainTeed does with Coal ash.

As we've begun to document, and as we will hammer into the ground in coming days, Coal ash can be employed to great good economic and environmental effect through it's use as a replacement for traditional raw materials in the making of Portland-type cement, with which we make structural concrete.

And, the CertainTeed company knows all about that, as well, as should our United States Environmental Protection Agency, since, as seen in:

Fiber Cement Siding - CertainTeed Learning Center; concerning:

"Use of Fly Ash in WeatherBoards (TM) Fiber Cement Siding; Fly ash is a key component used in the manufacture of CertainTeed’s fiber cement siding products.

The U.S. Environmental Protection Agency (EPA) recognizes fly ash as an industrial by-product of the coal combustion process in electricity-generating power plants.  The EPA supports the beneficial reuse of fly ash in construction applications because it is safe and reduces the amount of coal combustion residue sent to landfill.

In addition to its beneficial reuse in our fiber cement products, fly ash has been used in concrete since the 1930’s.  Most notably, it has been used in several construction projects and prominent buildings, including the Ronald Reagan Government Office building, home to the Environmental Protection Agency (EPA) in Washington, D.C.";

the US EPA itself is actually housed in a building made, in part, out of Coal fly ash.

We'll forego any attempt at colorful characterizations of the inherent irony, and return to the use of Coal fly ash in the making of "gypsum board", which is an entirely different animal than concrete made from cement.

The "gypsum" which comprises the mineral powder core of "wallboard", or "dry wall", has the chemical formula: "CaSO4-2H2O", and, is the chemically hydrated form of Calcium Sulfate, from which it is sometimes made.

And, it can, somewhat entertainingly, as revealed by:

Gypsum - Wikipedia, the free encyclopedia; wherein we're informed that:

"Synthetic gypsum is recovered via flue gas desulfurization at some coal-fired electric power plants. It can be used interchangeably with natural gypsum in some applications";.

be synthesized in some Coal-fired power plant exhaust gas scrubbers.

But, returning to the subject of fly ash itself, as we documented in:

Iowa Mines Metals from Coal Ash for the USDOE | Research & Development; concerning, for the most part: "US Patent 4,386,057 - Recovery of Iron Oxide from Coal Fly Ash" and "US Patent 4,397,822 - Process for the Recovery of Alumina from Fly Ash";

it is perfectly feasible to "mine" commercial quantities of valuable metals from Coal ash.

That is a topic we'll be riding into the ground in future reports, as well; which reports will also demonstrate that commodity metals like Aluminum and Iron, valuable as they might be, aren't the only metals that Coal ash can function as a source of.

Aluminum and Iron are, though, the major metallic components of Coal ash; and, numerous technologies have been developed to process Coal ash so that they can be recovered.

It is such a technology we bring to your attention in this dispatch, but, one with added value.

Scientists working in New Mexico have found that, in the course of recovering Aluminum and Iron from Coal ash, they can automatically convert the ash residue into, as West Virginia's US Senator Joe Manchin affirmed in the above-cited article from a Wheeling, WV, newspaper, to be possible, gypsum.

As seen in our excerpts from the initial link in this dispatch to:

"United States Patent 4,159,310 - Recovering Aluminum and Other Metal Values from Fly Ash

Date: June, 1979

Inventors: James Reynolds and Allan Williams, Colorado

Assignee: Public Service Company of New Mexico, Albuquerque, NM

Abstract: A process for recovering aluminum from fly ash containing iron, silicon and titanium which comprises: (a) chlorinating the fly ash in an oxidizing atmosphere to selectively chlorinate and vaporize iron chloride from the remaining chlorides, (b) chlorinating the residue from step (a) in a reducing atmosphere of carbon monoxide, in the presence of added silicon chloride to suppress the chlorination of silicon, and vaporizing the chlorides of aluminum, silicon, titanium, and the residual iron, (c) separating and recovering the vaporized chlorides by selective condensation, and treating the residue of step (b) with sulfuric acid to convert calcium chloride to gypsum, and to regenerate a chloridizing and binder solution for pelletizing fly ash feed.

Claims: A process for recovering aluminum from fly ash containing aluminum, iron and (silica) silicon which comprises: chlorinating the material by subjecting it to the action of chlorine at a temperature of about 500C to 1200C. in an oxidizing atmosphere in the presence of added oxygen in an amount equal to about 5-100 volume percent of the chlorine to selectively vaporize iron as iron chloride;

(That is, in fact, plenty hot; and, some significant amount of energy would have to be applied to the process. Waste heat recovered from a Coal-fired power plant could contribute to it, but, as suggested by:

Another Energy Bonanza for Coal Country | Research & Development; concerning, in part: "Geothermal Energy: Project Reveals Large, Green Energy Source in Coal Country; The Southern Methodist University's Geothermal Laboratory has increased its estimate of West Virginia’s geothermal generation potential to 18,890 megawatts (assuming a conservative 2% thermal recovery rate). The new estimate represents a 75 percent increase over estimates in Massachusetts Institute of Technology’s 2006 “The Future of Geothermal Energy” report and exceeds the state’s total current generating capacity, primarily coal based, of 16,350 megawatts; and:

USDOE Hydrogasifies Coal with Solar Power | Research & Development; concerning: "United States Patent 4,415,339 - Solar Coal Gasification Reactor; 1983; The USA, as represented by the Department of Energy; Abstract: Coal (or other carbonaceous matter, such as biomass) is converted into a duct gas that is substantially free from hydrocarbons. The coal is fed into a solar reactor, and solar energy is directed into the reactor onto coal char, creating a gasification front and a pyrolysis front. The product gas will be free of tar and other hydrocarbons, and thus be suitable for use in many processes;

we have some heat-providing options available that might help to conserve our Coal while tickling the pleasure centers of the environmentally sensitive among our citizens.)

(And) chlorinating the residue from (the initial) step by subjecting it to the action of chlorine at a temperature of about 500C to 1200C in a reducing atmosphere in the absence of solid carbon to vaporize the chlorides of aluminum and silicon; and separating and recovering the formed (reacted) chlorides from the vapors by selective condensing.

The process ... in which the reductive chlorination ... is performed in the presence of carbon monoxide as a reducing agent.

(Since Carbon Monoxide is needed to help things along, we remind you, that, as seen for just one instance in our report of:

Bayer Improves Coal + CO2 = Carbon Monoxide | Research & Development; concerning: "United States Patent 7,473,286 - Carbon Monoxide Generator; 2009; Assignee: Bayer Material Science, AG, Germany", which explains that: "Carbon monoxide gas is frequently produced in the art by means of a continuous process in which carbon-containing raw materials are reacted with oxygen and carbon dioxide";

we can make all of the Carbon Monoxide we might need for this New Mexico process for recovering Aluminum and other metals from Coal fly ash by reacting CO2, recovered from whatever handy source, with a little of our favorite "carbon-containing raw material". Coal, that is, if we have to spell it out.)

The process ... wherein the fly ash contains calcium and in which the material (residue of solid chlorides)  remaining after vaporization (of the metal chlorides) is reacted with sulfuric acid to produce disposable gypsum and to form hydrochloric acid.

(Note that they consider the "gypsum" to be "disposable", when, instead, it could be a by-product of at least commodity value, as in our above references concerning WV's US Senator Manchin's mention of Coal ash being "used in Marshall County by the CertainTeed company to make gypsum board".

Further, since "sulfuric acid" is required in this New Mexico process, note that, as can be seen in:

http://www.mcilvainecompany.com/Universal_Power/Subscriber/PowerDescriptionLinks/Erik%20Eriksson-Haldor%20Topsoe%20-%204-28-11; concerning the: "SNOX" (TM) process for purification of flue gas from combustion of high-sulfur fuels;

Denmark's rather well-known Haldor Topsoe company, who, as reported in:

Haldor Topsoe - Wikipedia, the free encyclopedia; "specialize in catalysts and catalytic processes",

have developed a technology capable of producing Sulfuric Acid on a commercial basis by scrubbing the flue gases of power plants that burn Sulfur-containing fuels.

And, further, note that, in the process of our subject, "United States Patent 4,159,310", after the desired metal chlorides have been extracted, when the residue is reacted with Sulfuric Acid to form Gypsum, some amount of "hydrochloric acid" acid is formed, which could be processed to allow recycling of needed Chlorine back into the initial reaction for the formation of the desired metal chlorides, thus affording some additional economies.)

The process ... in which titanium is present in said fly ash and it is chlorinated in accordance with step (b) and separated and recovered ... .

(As we believe we've previously documented, and as we will certainly document further in reports to follow, the valuable metal, Titanium" is also often present in Coal ash, in quantities sufficient to warrant recovery of it, especially if it can be produced in conjunction with the recovery of the more abundant metals, Iron and Aluminum.)

Description and Background: Large quantities of fly ash (consisting of) the combustion products of power plants burning pulverized coal exist throughout the country and more is being created by operation of these plants. This accumulation creates a disposal problem and represents a waste of metal values, particularly aluminum, as a typical fly ash contains up to fourteen percent aluminum by weight. Lesser amounts of iron, titranium and other useful metals are present in fly ash. 

No satisfactory process exists for economically recovering aluminum from fly ash having the required purity for commercial sale because of the difficulty of separating it from other metals present in the fly ash, particularly, iron.

Accordingly, it is a principal object of this invention to provide a method for recovering aluminum of substantially high purity from fly ash and other materials containing iron and silica with the aluminum. 

It is another object of this invention to provide a method for suppressing the chlorination of silicon when recovering aluminum as aluminum chloride from fly ash by chlorination. 

It is a further object of this invention to provide a method for the disposal of alkali and alkaline earth metal chlorides remaining in the final residue resulting from the chlorination of fly ash to recover aluminum as aluminum chloride.

(From experimental results presented, it) can be seen ... that from about 54 to about 77 percent of the aluminum, ...  and from about 50 to about 100 percent of iron (can be) recovered.

It is (also) seen from (those presented results) that an effective and economical process has been provided for recovering substantially pure aluminum, as well as other metal values, from fly ash by the selective chlorination and condensing procedure outlined above and shown ... . The process additionally provides a means for disposing of the alkali metal and alkaline earth chlorides in the residue with regeneration of hydrochloric acid which can be reused in the process. A maximum use of by-products and excess heat energy is achieved by the process of the invention."


So, we can, in an "economical process", extract most, and in some cases nearly all, of the Aluminum and the Iron in Coal fly ash.

When it's present, we can also extract Titanium as a by-product.

Further, as in "regeneration of hydrochloric acid which can be reused in the process", some of the major required reagents can be, to a certain extent, recovered and recycled back into the metal extraction process, thus improving economies and reducing pollution potentials.

And, don't forget that, after the desired metal chlorides have then been extracted from the Coal ash, the  remaining mineral residue can then be "reacted with sulfuric acid to produce ...gypsum", which "gypsum" just might find a market, as per West Virginia's US Senator Joe Manchin, in "Marshall County ... to make gypsum board".

Which "gypsum board", we remind you, is being made in Marshall County, WV, by the same company, CertainTeed, who claim, as in our introductory comments, to have helped to house the US Environmental Protection Agency in an office building that is, itself, made of concrete derived from cement that was based, at least in part, on Coal-fired power plant fly ash.

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